The requirements for conductive polymers used in the electronic and other industries are becoming more and more stringent. There is also an increasing need for materials which permit reduction in the size and weight of electronic parts and which themselves exhibit long-term stability and superior performance.
In order to satisfy these demands, active efforts have been made in recent years to develop new conductive macromolecular or polymeric materials. A number of proposals have also been made regarding the potential uses of such new compounds. For example, P. J. Nigrey et al. in Chem. Comm. pp. 591 et. seq. (1979) have disclosed the use of polyacetylenes as secondary battery electrodes. Similarly, in the J. Electro Chem. Soc., p. 1651 et seq. (1981) and in Japanese Patent Application Nos. 136469/1981, 121168/1981, 3870/1984, 3872/1984, 3873/1984, 196566/1984, 196573/1984, 203368/1984, and 203369/1984, have also disclosed the use of polyacetylenes, Schiff base-containing quinazone polymers, polarylene quinones, poly-p-phenylenes, poly-2,5-thienylenes and other polymeric materials as electrode materials for secondary batteries.
The use of polymeric materials in electrochromic applications has also been suggested, in, e.g., A. F. Diaz et al., J. Electroanal. Chem. 111: 111 et seq. (1980), Yoneyama et al., J. Electroanal. Chem. 161, p. 419 (1984) (polyaniline), A. F. Diaz et al., J. Electroanal. Chem. 149: 101 (1983) (polypyrrole), M. A. Druy et al., Journal de Physique 44: C3-595 (June 1983), and Kaneto et al., Japan Journal of Applied Physics 22(7): L412 (1983) (polythiophene).
These highly conductive polymers known in the art are typically rendered conductive through the process of doping with acceptors or donors. In acceptor doping, the backbone of the acceptor-doped polymer is oxidized, thereby introducing positive charges into the polymer chain. Similarly, in donor doping, the polymer is reduced, so that negative charges are introduced into the polymer chain. It is these mobile positive or negative charges which are externally introduced into the polymer chains that are responsible for the electrical conductivity of the doped polymers. In addition, such "p-type" (oxidation) or "n-type" (reduction) doping is responsible for substantially all the changes in electronic structure which occur after doping, including, for example, changes in the optical and infrared absorption spectra.
Thus, in all previous methods of doping the counterions are derived from an external acceptor or donor functionality. During electrochemical cycling between neutral and ionic states, then, the counterions must migrate in and out of the bulk of the polymer. This solid state diffusion of externally introduced counterions is often the rate-limiting step in the cycling process. It is thus desirable to overcome this limitation and thereby decrease the response time in electrochemical or electrochromic doping and undoping operations. It has been found that the response time can be shortened if the period required for migration of counterions can be curtailed. The present invention is predicated upon this discovery.